Siberian Bat

It is a small bat, with the length of its head and body only 39–51 mm (1.5–2.0 in). Its forearm is 33–39 mm (1.3–1.5 in) long; its tail is 32–44 mm (1.3–1.7 in) long; its hind feet are 7–9 mm (0.28–0.35 in) long; its ears are 12–17 mm (0.47–0.67 in). It has long fur relative to its body size. The fur on its back is pale brown with a golden sheen, while the fur on its ventral side is paler gray, sometimes with a yellowish tinge. Its tragus is narrow and pointed.

It is found throughout much of the Palearctic east of the Ob River, from eastern Kazakhstan east throughout southern Siberia to the Kamchatka Peninsula, and south to northern China, northern Mongolia, North Korea, and northern South Korea. It is also known from Sakhalin & the Kuril Islands in Russia, and Hokkaido in Japan. It inhabits both lowland and mountain forests as well as forest-steppe ecosystems. During the summer it takes shelter in tree hollows, caves, and even buildings, but it winters exclusively in caves.

During the summer, females will form maternity colonies to raise their young. The litter size is one pup, though occasionally two are born. Pups are born in early summer, with pups becoming volant around one month of age. Maternity colonies are frequently in manmade structures.